Do smelly fish make better friends?

How do you win friends and influence people? Pay for dinner at a restaurant? Adopt a considerate approach to colleagues? Try an expensive new perfume? It seems that in the fish world making friends depends on how smelly you are! In a report to be published in May in Animal Behaviour, researchers at Glasgow University and the FRS Freshwater Laboratory at Pitlochry have shown that Scottish salmon are much more likely to fight each other when their smells are concentrated, for example in pools rather than fast-flowing rivers.

The responses of fish to one another's smells can depend on whether the fish are related. Brothers and sisters are able to recognize the odour of friendly family members and therefore choose not to fight one another. However, the strong smell of some fish betrays them as being unrelated and unfriendly, and battle commences. It's all about protection of genes for future generations; brothers and sisters don't waste their time and energy fighting, which means they are able to concentrate on the important things in life - like growing and maturing sufficiently to produce offspring
"It's amazing! Fish are obviously much cleverer than we've given them credit for in the past," says Dr Si'?n Griffiths, a member of the research team that made the discovery.

"Traditionally fish have been thought of as simple and unsophisticated, but these salmon can actually recognize each other, and actively decide to be nicer to their siblings." Her colleague Dr John Armstrong agrees that the old wives tale of goldfish with no brainpower will have to be updated.

But why should we be interested in the brainpower of salmon? Many species of fish, such as salmon guard territories for much of their lives. However, energy spent chasing away intruders means that less energy is available for growth. So it is in the interest of fish (and fishmongers)
that brothers and sisters are kept together because fish that are less aggressive grow bigger and live longer.

The research has fisheries management implications. Fish farmers can help their fish conserve energy - and promote growth - by keeping brothers and sisters together. However, for managers restoring fisheries, the decision of whether to stock family members into a river together will depend on the type of habitat, and the likelihood of smells becoming concentrated.